Changes in ENSO and Interdecadal Climate Variability in the Holocene Recorded in Fossil Corals
Abstract
Annually-banded corals living on the north coast of Papua New Guinea record changes in SST and salinity in the stable isotopic and trace element composition of their skeletons. Previously, we exploited these attributes and the presence of abundant fossil corals to investigate changes in ENSO over the last glacial-interglacial cycle. Here we focus on more detailed analysis of the Holocene interval based on a total of about 400 years of new, near-monthly-resolved, isotopic and trace element coral data from the interval from about 9,500 to 6,500 years BP. Our findings include: INTERANNUAL ENSO VARIABILITY: The amplitude of ENSO-related variability in skeletal δ18O is reduced to about 30% of Modern and late Holocene values in corals from 9.1-9.4 ka through to 6.5 ka. These results support previous inferences of weakened ENSO variability in the early-mid-Holocene. MEAN CONDITIONS: Based on a combination of trace element and δ18O analysis, our initial results suggest that SST was similar to present at around 9.1-9.4 ka. Mean salinity, however, appears to have been higher in the earlier period, similar to what is experienced today during El Niño events. These observations contrast with some previous suggestions of general La Niña-like conditions in the early Holocene based on eastern equatorial Pacific data. INTERDECADAL VARIABILITY: Interdecadal variability in skeletal δ18O of modern corals from the region appears to record salinity changes associated with the Pacific Decadal Oscillation. In our fossil corals, we find that the amplitude of this interdecadal variability is reduced in the early-mid-Holocene, when interannual ENSO-related variability is also weak. These observations lend some support to the suggestion that much of the modern-day PDO variability is related to ENSO, and, therefore, is not a separate mode of climate variability.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2005
- Bibcode:
- 2005AGUFMPP53A..03T
- Keywords:
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- 1833 Hydroclimatology;
- 3334 Middle atmosphere dynamics (0341;
- 0342);
- 3339 Ocean/atmosphere interactions (0312;
- 4504);
- 4215 Climate and interannual variability (1616;
- 1635;
- 3305;
- 3309;
- 4513)